Field
The present disclosure relates to a crystal form of methyl 3-chloro-5-(4,6-dimethoxypyrimidin-2-ylcarbamoylsulfamoyl)-1-methylpyrazole-4-carboxylate (halosulfuron-methyl), to its preparation processes and to its use in agrochemical preparations.
Description of Related Art
Halosulfuron-methyl (methyl 3-chloro-5-(4,6-dimethoxypyrimidin-2-ylcarbamoylsulfamoyl)-1-methylpyrazole-4-carboxylate) is from the sulfonylurea group of chemicals and used as herbicide. Halosulfuron-methyl has a wide herbicide activity spectrum for controlling weeds such as perennial grasses and broadleaf weeds either for pre or post emergence treatment. The active ingredient is absorbed by the root system and/or leaf surface of the weed species and works by inhibiting the AcetoLactate Synthase (ALS) enzyme which is responsible for the synthesis of proteins required for cell division and plant growth, and hence, the weeds will start discolor and die within few days after the treatment.
Halosulfuron-methyl has molecular formula of C13H15ClN6O7S. Its chemical structure is

The commercially available halosulfuron-methyl, which is usually manufactured by the process described in U.S. Pat. No. 4,668,277, is present in an amorphous state. It has been found that halosulfuron-methyl in amorphous state is highly viscous, which is not suitable for being prepared as compositions or formulations having spray equipment cleanout property. Halosulfuron-methyl residues stay in the spray equipment after spraying. Adequate cleanout may require a rinsing procedure that is not only time-consuming but also results in wastewater disposal problem. Therefore, there is a need to provide a novel form of halosulfuron-methyl with increased solubility and decreased viscosity.